The viral disease causes direct losses to U.S. swine producers to the tune of $664 million a year.

Unlike the current live vaccines used to prevent PRRS, the new vaccine uses an inactivated virus to eliminate adverse reactions in pigs such as abortion, sick piglets and further spread of the disease, said Renukaradhya Gourapura, an associate professor in the university’s Food Animal Health Research Program, part of the Ohio Agricultural Research and Development Center.

The new vaccine is also enclosed in biodegradable nanoparticles, which improves its efficacy and its absorption by a pig’s immune system.

100% protection

“Our tests have shown that two doses of this vaccine, administered intranasally along with a potent mucosal adjuvant, achieve 100 percent protection in pigs against genetically variant PRRS virus,” said Gourapura, who started working on this project in 2009.

“Current PRRS virus vaccines are injected in the muscle, but this method of vaccination induces very little immunity in the respiratory system, where it’s actually needed,” he said. ”Applying the vaccine through the nose ensures that it goes directly into the respiratory system, where it’s better taken up by immune cells and induces adequate local mucosal immunity against the virus.”

Pioneering work

A patented technology, the nanoparticle-based PRRS virus vaccine is made from a biodegradable polymer of lactic acid and glycolic acid, known as PLGA. PLGA is an agent approved by the U.S. Food and Drug Administration for use in human vaccines and cancer drug-delivery systems.

This is the first time the PLGA-based nanotechnology is being used with food animals.

“Our vaccine has proven to be completely safe in tests so far, with no side effects associated with it,” Gourapura said. “The use of nanoparticles allows the vaccine to stay in the pig’s system for four to eight weeks without being degraded.”

The vaccine is also shelf-stable. Gourapura tested it for one year without showing any loss of quality.

Ongoing problem

First recognized in the United States in 1987, the PRRS virus responsible for the disease was isolated by OARDC associate director David Benfield (then at South Dakota State University) and others in 1992.

Now, PRRS is estimated to be present in 60 percent of U.S. herds. Symptoms include fever, respiratory distress, anorexia and weakening of the immune system that makes pigs more susceptible to other infections. In pregnant sows, it causes abortion.

In Ohio, which ranks ninth in the U.S. in overall pork production, according to the National Pork Board, outbreaks of PRRS have been more common since 2010.

Even among vaccinated sow herds in the state, the virus can cause 10-20 percent mortality, a significant economic loss for an industry worth $681.5 million in production value alone.

Field trials next

Gourapura said the vaccine has been successfully tested in a small number of animals at Ohio State. The next step involves extensive field trials in hundreds of pigs in commercial herds.

“The vaccine appears to be commercially feasible,” he said. “Once it is produced in large quantities, its cost should be similar or just a little more than that of currently available vaccines for PRRS.”

Gourapura said his vaccine could also become a model for the development of similar nanoparticle-encapsulated vaccines for other diseases affecting pigs and other food-producing animals.

This research project has been supported by several grants from the National Pork Board, the U.S. Department of Agriculture’s PRRS CAP2 project and OARDC, totaling over $500,000.